A Russian plane carrying the body of the ambassador assassinated in Turkey landed in Moscow today. Andrei Karlov's coffin and his widow travelled back to Russia after the veteran diplomat was shot dead by a 22-year-old Turkish policeman at an art exhibit in Ankara on Monday.<br/><br/>Meanwhile, a Russian investigators arrived in Turkey today to probe the assassination of Moscow's ambassador, as both sides pledged the murder would not damage improving relations. Russian investigative team also visited the scene of the attack at the Contemporary Arts Centre as part of a joint probe with Turkey.<br/><br/>'According to Turkish media, six people have been detained over the Karlov assassination, including the sister, mother and father of the 22-year-old Altintas.<br/><br/>'Turkey has already been on high alert after a string of deadly attacks. Russian President Vladimir Putin also ordered his secret services to boost security at home and abroad, and to step up cooperation with foreign intelligence services. <br/><br/>'<br/>